1. Field of the Invention
This invention relates to photography, and more particularly, it relates to an improvement in multicolor photographic images prepared by processes which utilize, as the image dye-providing material, a compound capable of undergoing cleavage in the presence of an imagewise distribution or silver ion and/or soluble silver complex to liberate a corresponding imagewise distribution of color-providing moiety, e.g., a dye.
2. Description of the Prior Art
U.S. Pat. No. 3,719,489 describes and claims photographic processes employing initially photographically inert compounds which are capable of undergoing cleavage in the presence of the imagewise distribution of silver ions made available during processing of a silver halide emulsion to liberate a reagent, such as, a photographically active reagent or a dye in an imagewise distribution corresponding to that of said silver ions. In one embodiment disclosed therein, color images are produced by using as the photographically inert compounds, color-providing compounds which are substantially non-diffusible in the photographic processing composition but capable of undergoing cleavage in the presence of the imagewise distribution of silver ions and/or soluble silver complex made available in the undeveloped and partially developed areas of a silver halide emulsion as a function of development to liberate a more mobile and diffusible color-providing moiety in an imagewise distribution corresponding to the imagewise distribution of said ions and/or said complex. The subsequent formation of a color image is the result of the differential in diffusibility between the parent compound and liberated color-providing moiety whereby the imagewise distribution of the more diffusible color-providing moiety released in the undeveloped and partially developed areas is free to transfer and form a color image, e.g., in a superposed image-receiving layer.
Compounds disclosed as useful in liberating a reagent in the presence of said silver ions and/or silver complex are sulfur-nitrogen compounds containing the group --S--X--N-- or --S--X--N.dbd. wherein X is ##STR1## These 1,3-sulfur-nitrogen compounds may be linear or cyclic in structure, and in a particularly preferred embodiment are cyclic in structure, for example, thiazolidine compounds which comprise a dye radical having the chromophoric system of an azo, anthraquinone, phthalocyanine or other dye and a thiazolidin-2'-yl moiety which may be bonded directly to the dye radical or through an appropriate linking group.
U.S. Pat. No. 4,060,714 also is concerned with the preparation of multicolor photographic images utilizing the above-denoted color-providing compounds and discloses the use of a silver ion scavenger layer between adjacent silver halide layers to enhance color separation. Materials disclosed as useful as the non-diffusible silver halide scavengers include silver complexing agents and compounds that generate silver complexing agents which form stable complexes with silver ion and silver precipitating agents that reduce silver ion to metallic silver.
The present invention is concerned with an improvement in photographic processcs of the aforementioned type which employ compounds capable of undergoing silver ion cleavage in an imagewise fashion to provide a corresponding imagewise distribution of a color-providing moiety.